to be. The second impulse is not much better—to use the oldest copy out of several of different date. In theory, and very often in practice, the relative age of the copies is of no importance; a sixteenth-century manuscript which reproduces a good lost copy of the eleventh century is much more valuable than a faulty and retouched copy made in the twelfth or thirteenth century. The third impulse is still far from being good; it is to count the attested readings and decide by the majority. Suppose there are twenty copies of a text; the reading A is attested eighteen times, the reading B twice. To make this a reason for choosing A is to make the gratuitous assumption that all the manuscripts have the same authority. This is an error of judgment; for if seventeen of the eighteen manuscripts which give the reading A have been copied from the eighteenth, the reading A is in reality attested only once; and the only question is whether it is intrinsically better or worse than the reading B.
It has been recognised that the only rational procedure is to begin by determining in what relation the copies stand to each other. For this purpose we adopt as our starting-point the incontrovertible axiom that all the copies which contain the same mistakes in the same passages must have been either copied from each other or all derived from a copy containing those mistakes. It is inconceivable that several copyists, independently reproducing an original free from errors, should all introduce exactly the same errors; identity of errors attests community of origin. We shall cast aside without scruple all the copies derived from a single manuscript which has been preserved.